This invention relates broadly to an assembly for detecting defects in articles of manufacture and more specifically, relates to a method and apparatus for automatically detecting defects in glassware.
It is oftentimes necessary to monitor articles of manufacture to assure that desired product quality levels are achieved. It is readily apparent, for example, to those having knowledge in the manufacture of glassware that finished glassware products may not be perfectly formed and may therefore in some cases not be entirely suitable for the use intended. By providing monitoring or inspection devices to eliminate those articles of manufacture which are not entirely suitable and therefore considered defective for a specific use, product quality can be enhanced. In glassware "spikes" which are sharp glass projections formed in glassware and "birdswings" which are found generally in bottles and which comprise thin pieces of glass extending across opposite inner walls thereof are examples of items for which glassware is often inspected and glassware rejected if present. Obviously, monitoring or inspection systems and a degree of reliability inherent in any such system for monitoring unwanted characteristics in finished glassware products or other such articles of manufacture are often important in achieving quality of the product.
Heretofore monitoring systems for detecting defects in glassware have taken various forms ranging from, for example, mere visual inspection utilized in the slow production of glassware to complex electronic detection systems utilized in the more rapid production of glassware.
As an example of an early electronic inspection device, Fedorchak disclosed in U.S. Pat. No. 2,649,500 a glass inspection apparatus wherein ultraviolet light was directed into the inside of a bottle. The ultraviolet light was reflected out of the bottle onto a mosaic which was in turn scanned by a cathode-ray tube. The cathode-ray tube scanned the mosaic in a spiral manner to thereby provide an indication when a flaw, such as a sharp projection, occurred in the bottle. This apparatus had the drawback in that a lamp had to be positioned such that light could be directed into the inside of the bottle so that the light would be reflected therefrom. This prohibited rapid assembly line inspecting of bottles. In addition, no means were taken into account for the change in reflected ultraviolet light due to the corners of the glass jar and for other normal variances in the contour of the bottle caused by, for example, seams and lettering.
A more recent development was disclosed by Gambrell et al in U.S. Pat. No. 3,379,829 wherein a fault detection apparatus was disclosed wherein normal perturbations in the glassware were not detected because a mask corresponding to the shape of the inspected article of manufacture provided blanking signals when normally encountered perturbations on the surface were scanned by an electronic beam. Such an arrangement, however, requires that the mask be appropriately aligned with the article being inspected and eliminates the possibility of checking flaws positioned between the masked portion of the article and the source of radiation which is detected.
Richards disclosed in U.S. Pat. No. 2,798,605 an electronic inspection apparatus for detecting foreign matter in bottles. In the Richards' invention, bottles are passed along a conveyor line and are passed in front of the optical system of a television camera. As each object passes in front of the camera, a light flash of short duration is provided to thereby illuminate the object and cause an image to be transmitted to the mosaic of the television camera tube. The mosaic is scanned by the cathoderay gun of the camera tube which provides an output signal that indicates appreciable discontinuity of the video signal from its average level. However, this invention requires a rather complex "herringbone" sweep action in order for the inspection apparatus to distinguish between the sides of the bottle and true defects. Further, two transverse views are required of each bottle in order to detect flaws along the vertical length of the bottle, thereby requiring two separate camera systems. Thus, while Richards was an improvement in the art, the method and apparatus required for inspecting the bottles remained quite complex.
In U.S. Pat. No. 3,746,784, issued to the inventor of the present invention and assigned to the common assignee herewith, an electronic defect detecting apparatus was disclosed which included a video camera for scanning bottles as they passed in front of the camera. Circuitry was provided for eliminating the signals caused by the leading and trailing edges of the bottles so that these signals would not be considered as defects. However, this invention was designed to inspect flint glass and could not accurately and reliably inspect all types of bottles or flasks, including colored bottles or bottles with lettering or coloration. In addition, the invention disclosed in the '784 patent could not accurately inspect the bottoms of round bottles. It therefore has been found that none of the monitoring systems currently being used are completely satisfactory in providing a system which has the necessary accuracy, reliability, versatility and/or speed required for today's modern methods of mass producing articles of manufacture and more specifically, glassware.
It therefore is an object of the present invention to provide a new and improved method and apparatus for monitoring and detecting defects in articles of manufacture such as glassware which is more dependable and accurate than those found in the prior art.
Another object of the present invention is to provide a new and improved method and apparatus for electronically monitoring and detecting defects in glassware having lettering, seams and/or other normal imperfections.
Yet another object of the present invention is to provide an improved method and apparatus for detecting flaws in colored glassware wherein both the sides and the bottom of the glassware may be inspected but wherein lettering, mold marks, coloring and minor imperfections are discriminated with respect to flaws in the glassware.